U.S. patent application number 10/048993 was filed with the patent office on 2002-08-08 for turbo compressor and refrigerator with the compressor.
Invention is credited to Koga, Jun.
Application Number | 20020106278 10/048993 |
Document ID | / |
Family ID | 18685586 |
Filed Date | 2002-08-08 |
United States Patent
Application |
20020106278 |
Kind Code |
A1 |
Koga, Jun |
August 8, 2002 |
Turbo compressor and refrigerator with the compressor
Abstract
A turbo-type compressor having an improved performance which may
be produced without increasing its size or cost, and the
performance of a refrigeration unit is also improved when it is
provided with such a turbo-type compressor. The turbo-type
compressor includes a casing (55) provided with an intake opening
and a discharge opening; a rotation shaft (41) operated by a
driving mechanism; an impeller (19) provided integrally with the
rotation shaft (41); a diffuser section (46) constituted by a pair
of a first wall section (56) and a second wall section (58),
located at the outer periphery side of the impeller (19) to serve
as a fluid passage for a refrigerant driven towards the outer side
by the rotation action of the impeller (19). The refrigerant is
drawn in through the intake opening, by the action of the impeller
(19) which is rotated together with the rotation shaft (41) and
driven by a motor, to be compressed and discharged through the
outlet opening. In this compressor, the diffuser section (46) is
constructed in such a way that the width dimension in the axial
direction of the outlet opening (46b) is made larger than the width
dimension of the inlet opening (46a).
Inventors: |
Koga, Jun; (Takasago-shi,
JP) |
Correspondence
Address: |
OBLON SPIVAK MCCLELLAND MAIER & NEUSTADT PC
FOURTH FLOOR
1755 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Family ID: |
18685586 |
Appl. No.: |
10/048993 |
Filed: |
February 19, 2002 |
PCT Filed: |
June 18, 2001 |
PCT NO: |
PCT/JP01/05171 |
Current U.S.
Class: |
415/211.2 |
Current CPC
Class: |
F25B 2400/13 20130101;
F25B 1/10 20130101; F05D 2250/52 20130101; F25B 1/053 20130101;
F04D 17/122 20130101; F04D 29/441 20130101; F25B 31/008
20130101 |
Class at
Publication: |
415/211.2 |
International
Class: |
F01D 001/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 20, 2000 |
JP |
2000-185239 |
Claims
1. A refrigeration apparatus, comprising: a compressor for
compressing a refrigerant admitted from an intake opening and
discharging the refrigerant from a discharge opening; a condenser
for condensing and liquefying the refrigerant and forwarding a
resultant liquefied refrigerant; a throttling mechanism for
reducing the pressure of the liquefied refrigerant; and a vaporizer
for cooling an object to be cooled by exchanging heat between the
object to be cooled and a resultant condensed and pressure-reduced
liquefied refrigerant, and evaporating and vaporizing the liquefied
refrigerant, wherein the compressor is a turbo-type compressor
comprising: a casing provided with an intake opening and a
discharge opening; a rotation shaft operated by a driving
mechanism; an impeller provided integrally with the rotation shaft;
a diffuser section comprised of a pair of wall sections at outer
peripheries of the impeller to serve as a fluid passage for a fluid
driven towards the outer periphery side by the rotation of the
impeller so that the fluid is drawn in from the intake opening, by
the action of the impeller which is rotated together with the
rotation shaft and driven by the driving mechanism, to be
compressed and discharged from the discharge opening through the
diffuser section; wherein the diffuser section is formed in such a
way that the width dimension in the axial direction of an outlet
opening located at the outer periphery side is made larger than the
width dimension of an inlet opening for the fluid which is driven
by the impeller.
2. A refrigeration apparatus according to claim 1, wherein the
width dimension of the outlet opening is made larger than the width
dimension of the inlet opening without altering the area ratio of
the inlet opening to the outlet opening of the diffuser
section.
3. A refrigeration apparatus according to claim 1, wherein the pair
of wall sections forming the diffuser section is made in a tapered
shape so as to separate gradually from each other from the inlet
opening towards the outlet opening.
4. A refrigeration apparatus according to claim 1, wherein one of
the pair of wall sections forming the diffuser section is made into
a tapered shape so as to separate gradually from the other one of
the pair of wall sections from the inlet opening towards the outlet
opening.
5. A refrigeration apparatus according to claim 1, wherein the
turbo-type compressor is a multi-stage compressor having a
plurality of the impellers and compresses the fluid from the intake
opening sequentially by using, first, an upstream-side impeller,
and successive impellers afterward.
Description
TECHNICAL FIELD
[0001] The present invention relates to a turbo-type compressor
used for compressing liquids by a rotating impeller, and relates to
a refrigeration apparatus having the compressor.
BACKGROUND ART
[0002] Conventionally, a turbo-type compressor is used in
refrigeration apparatuses as a means of compressing refrigerant.
The turbo-type compressor compresses a fluid by rotating a rotation
shaft provided with an impeller.
[0003] The structure of a conventional turbo-type compressor will
be explained with reference to FIG. 10.
[0004] As shown in the figure, an impeller 3 having a plurality of
vanes 2 arranged in a circumferential direction with spaces
therebetween is attached to a rotation shaft 1 of the turbo-type
compressor so that the vanes can be rotated with the rotation shaft
1. A rotor constituted by the rotation shaft 1 and the impeller 3
is housed inside a casing 4.
[0005] The interior of the casing 4 is divided by a partition plate
5 into a diffuser section 6 and a return passage 7, and the
diffuser section 6 and the return passage 7 are communicated with a
return bend section 8 having U-shaped cross section.
[0006] The diffuser section 6 is constituted by a first wall
section 4a on the casing side and a second wall section 5a on the
partition plate side, and the first wall section 4a and the second
wall section 5a are oriented perpendicular to the rotation shaft 1
while being parallel to each other. Also, a plurality of return
vanes 9 are spaced circumferentially so as to guide the flowing
fluid.
[0007] In this turbo-type compressor, the fluid compressed by the
impeller 3 and output to the diffuser section 6 is forwarded to the
return passage 7 through the return bend section 8.
[0008] In such a compressor, the diffuser section 6 comprised by
the first wall section 4a and the second wall section 5a serves to
decelerate the flow of the fluid driven by the impeller 3 and
recovers most of the dynamic pressure as static pressure, and the
pressure recovery coefficient Cp, which is a parameter to indicate
the performance of the turbo-type compressor, is influenced by the
shape of the diffuser section 6.
[0009] Therefore, the pressure recovery coefficient Cp may be
increased by improving the area and shape of the inlet opening 6a
and outlet opening 6b of the diffuser section 6.
[0010] However, in a conventional compressor, as shown in the graph
in FIG. 11, the pressure recovery coefficient Cp has not reached a
value of 0.5, thus leaving room for further improvement. For this
reason, there are demands to improve the performance of the
turbo-type compressor by modifying the pressure recovery
coefficient Cp in the diffuser section 6.
[0011] Here, the pressure recovery coefficient Cp is expressed by
the aspect ratio and the area ratio of the inlet and outlet
openings 6a and 6b of the diffuser section 6.
[0012] The aspect ratio and the area ratio are obtained according
to the following expressions:
Aspect ratio is given by 2.DELTA.R/b2=2(R2-R1)/b2 (1)
Area ratio is given by AR-1=(R2b2/R1b1)-1 (2)
[0013] where
[0014] R1 is a radius at the inlet opening 6a of the diffuser
section 6;
[0015] R2 is a radius at the outlet opening 6b of the diffuser
section 6;
[0016] b1 is a width dimension of the inlet opening 6a of the
diffuser section 6; and
[0017] b2 is a width dimension of the outlet opening 6b of the
diffuser section 6.
[0018] Also, the pressure recovery coefficient Cp for the diffuser
section 6 is represented by the following expression:
pressure recovery coefficient Cp=(Ps2-Ps1)/(Pt1-Ps1)
[0019] where
[0020] Ps1 is a static pressure at the inlet opening 6a of the
diffuser section 6;
[0021] Ps2 is a static pressure at the outlet opening 6b of the
diffuser section 6; and
[0022] Pt1 is a total pressure at the inlet opening 6a of the
diffuser section 6.
[0023] It can be seen that the level of recovery of the dynamic
pressure into static pressure of the fluid, which is compressed and
output by the impeller 3, can be improved by an amount
corresponding to an increase in the pressure recovery coefficient
Cp.
[0024] The present invention takes into consideration the
above-mentioned circumstances, and objects thereof include
providing a high efficiency turbo-type compressor having improved
performance without increasing the size of the compressor, and
providing a refrigeration apparatus including such a turbo-type
compressor.
DISCLOSURE OF INVENTION
[0025] In order to achieve the above objects, the present invention
provides a turbo-type compressor comprising a casing provided with
an intake opening and a discharge opening; a rotation shaft
operated by a driving mechanism; an impeller provided integrally
with the rotation shaft; a diffuser section formed by a pair of
wall sections at outer peripheries of the impeller to serve as a
fluid passage for a fluid driven towards the outer periphery side
by the rotation of the impeller so that the fluid is drawn in from
the inlet opening, by the action of the impeller which is rotated
together with the rotation shaft and driven by the driving
mechanism, to be compressed and discharged from the discharge
opening through the diffuser section; wherein the diffuser section
is formed in such a way that the width dimension in the axial
direction of an outlet opening located at the outer periphery side
is made larger than the width dimension of an inlet opening for the
fluid which is driven by the impeller.
[0026] Accordingly, because the width dimensions of the openings in
the axial direction of the inlet side and the outlet side are made
so that the outlet side is larger relative to the inlet side, the
aspect ratio of the inlet side and the outlet side is made somewhat
smaller and the area ratio is made larger, so that the pressure
recovery coefficient in the diffuser section can be made larger.
This design enables effective recovery of the dynamic pressure of
the compressed fluid output from the impeller into a static
pressure in the diffuser section without making the structure
larger or more complex, and accordingly, a high compression
efficiency is realized in the turbo-type compressor of the present
invention.
[0027] In another aspect of the invention, in the turbo-type
compressor described above, the width dimension of the outlet
opening is made larger than the width dimension of the inlet
opening without altering the area ratio of the inlet opening to the
outlet opening of the diffuser section.
[0028] Accordingly, without altering the area ratio of the inlet
opening to the outlet opening in the diffuser section, the width
dimension of the outlet opening is made larger relative to the
width dimension of the inlet opening. That is, because the radius
of the outlet opening is reduced by an amount corresponding to the
increase in the width dimension of the outlet opening, the outer
radius can be made smaller and the cost of the compressor can be
reduced.
[0029] Also, even if the area ratio of the inlet opening to the
outlet opening is not altered, because the width dimension of the
outlet opening is made larger relative to that of the inlet
opening, the aspect ratio is reduced, and the pressure recovery
coefficient is made larger so as to reliably improve the
performance.
[0030] In yet another aspect of the invention, in the turbo-type
compressor described above, the pair of wall sections forming the
diffuser section is tapered so as to separate gradually from each
other from the inlet opening towards the outlet opening.
[0031] That is, by tapering the pair of wall sections forming the
diffuser section, the performance of the compressor is readily
improved by enlarging the width dimension of the outlet opening
relative to that of the inlet opening. Also, because the wall
sections are tapered, it is possible to avoid the problem of stream
separation in the diffuser section of the refrigerant output from
the impeller.
[0032] In yet another aspect of the invention, in the turbo-type
compressor described above, one of the wall sections forming the
diffuser section is formed into a tapered shape so as to separate
gradually from the other one of the pair of wall sections from the
inlet opening towards the outlet opening.
[0033] In other words, by making only one of the wall sections that
constitute the diffuser section, into a tapered shape, the
performance of the compressor can be improved quite readily by
increasing the width dimension of the outlet opening relative to
the inlet opening. Also, because only one of the wall sections
needs to be made into a tapered shape, the performance can be
improved even more easily.
[0034] In particular, by tapering the wall section in the front
side which has more space as compared with the rear side of the
impeller having a downstream side passage that communicates with
the diffuser section, the dimension in the axial direction can be
made smaller.
[0035] In yet another aspect of the invention, in the turbo-type
compressor described above, the compressor is a multi-stage
compressor having a plurality of the impellers and compresses the
fluid from the intake opening sequentially by using, first, an
upstream-side impeller first, and successive impellers
afterward.
[0036] In other words, the present multi-stage impeller provides a
superior turbo-type compressor of high performance because the
pressure recovery coefficient is improved in each stage of
compression by respective impellers at the respective diffuser
sections serving as the fluid path for the fluid output by the
respective impellers.
[0037] The refrigeration apparatus according to the present
invention includes a compressor for compressing a refrigerant
admitted from an inlet opening and discharging the refrigerant from
a discharge opening; a condenser for condensing and liquefying the
refrigerant and forwarding a liquefied refrigerant; a throttling
mechanism for reducing the pressure of the liquefied refrigerant; a
vaporizer for cooling an object to be cooled by exchanging heat
between the object to be cooled and a resultant condensed and
pressure-reduced liquefied refrigerant, and evaporating and
vaporizing the liquefied refrigerant, wherein the compressor is a
turbo-type compressor described above.
[0038] In the present refrigeration apparatus, because a high
efficiency turbo-type compressor, having a diffuser section that
exhibits high performance and produces a high recovery coefficient,
is used as a compressor to compress the refrigerant and to output
the compressed refrigerant to the condenser, the cooling efficiency
can be improved significantly, and accordingly, the refrigeration
apparatus can produce superior cooling performance.
BRIEF DESCRIPTION OF DRAWINGS
[0039] FIG. 1 is a perspective view to explain the structure and
construction of a turbo-type compressor in an embodiment of the
present invention and a refrigeration apparatus having the
compressor.
[0040] FIG. 2 is a schematic diagram to explain the structure of
the turbo-type compressor and the refrigeration apparatus having
the compressor in the embodiment of the present invention.
[0041] FIG. 3 is a cross sectional view of the turbo-type
compressor to explain the construction of the turbo-type compressor
according to the embodiment of the present invention.
[0042] FIG. 4 is a cross sectional view of a compression section to
explain the construction of the turbo-type compressor according to
the present invention.
[0043] FIG. 5 is a graph showing the performance of a diffuser
section of the turbo-type compressor according to the embodiment of
the present invention.
[0044] FIG. 6 is a cross sectional view of the compression section
to explain the construction of a turbo-type compressor according to
another embodiment of the present invention.
[0045] FIG. 7 is a graph showing the performance of the diffuser
section of the turbo-type compressor according to the another
embodiment of the present invention.
[0046] FIG. 8 is a cross sectional view to explain the construction
of the turbo-type compressor according to yet another embodiment of
the present invention.
[0047] FIG. 9 is a cross sectional view of the compression section
of the turbo-type compressor according to still another embodiment
of the present invention.
[0048] FIG. 10 is a cross sectional view to explain the
construction of a conventional turbo-type compressor.
[0049] FIG. 11 is a graph showing the pressure recovery coefficient
at the diffuser section.
BEST MODE FOR CARRYING OUT THE INVENTION
[0050] A turbo-type compressor and a refrigeration apparatus
provided with the turbo-type compressor according to an embodiment
of the present invention will be described with reference to the
attached drawings.
[0051] An overall structure of the refrigeration apparatus will be
explained first with reference to FIGS. 1 and 2.
[0052] The refrigeration apparatus shown in the figures includes a
vaporizer 11 for cooling the cold water by means of heat exchange
between the refrigerant and the cold water and for evaporating and
vaporizing the refrigerant; a compressor 12 for compressing the
refrigerant vaporized in the vaporizer 11; a condenser 13 for
condensing and liquefying the refrigerant compressed in the
compressor 12; a throttle valve 14 for reducing the pressure of the
refrigerant liquefied in the condenser 13; an intermediate cooler
15 for temporarily storing and cooling the refrigerant liquefied in
the condenser 13; and an oil cooler 16 for cooling the lubricating
oil for the compressor 12 by utilizing a portion of the refrigerant
cooled in the condenser 13.
[0053] Also, a motor (a driving mechanism) 17 is connected to the
compressor 12 for operating the compressor 12.
[0054] The vaporizer 11, the compressor 12, the condenser 13, the
throttle valve 14 and the intermediate cooler 15 are connected via
a primary piping 18 to constitute a closed system in which the
refrigerant is circulated.
[0055] The compressor 12 is based on a 2-stage (multistage)
centrifugal compressor, a so-called turbo compressor, and this
turbo compressor 12 is provided with a plurality of impellers 19.
The refrigerant is compressed in a first stage impeller 19a
situated in the upstream side of the impeller 19, and the
compressed refrigerant is led into the second stage impeller 19b to
be compressed further and is then sent to the condenser 13.
[0056] The condenser 13 includes a main condenser 13a and a
sub-cooler 13b which is an auxiliary compressor, and the
refrigerant is introduced first to the main condenser 13a and then
to the sub-cooler 13b. However, a portion of the refrigerant cooled
in the main condenser 13a is introduced into the oil cooler 16,
without passing through the sub-cooler 13b, to cool the lubricating
oil.
[0057] Also, apart from the above process, a portion of the
refrigerant cooled in the main condenser 13a is introduced into the
casing 31 of the motor 17, which will be explained later, without
passing through the sub-cooler 13b, and cools stators and coils
which are not shown in the diagram.
[0058] The throttle valve 14 is disposed between the condenser 13
and the intermediate cooler 15, and between the intermediate cooler
15 and the vaporizer 11, and they are used for stepwise reduction
of the pressure of the refrigerant liquefied in the condenser
13.
[0059] The structure of the intermediate cooler 15 is equivalent to
a hollow vessel, and the refrigerant which has been cooled in the
main condenser 13a and the sub-cooler 13b and reduced in pressure
in the throttle valve 14, is temporarily stored therein and is
subjected to further cooling. Here, the vapor phase components in
the intermediate cooler 15 are introduced into the second stage
impeller 19b of the compressor 12 through the bypass piping 23,
without passing through the vaporizer 11.
[0060] The turbo-type compressor 12 provided for the
above-mentioned refrigeration apparatus will be further explained
in detail below.
[0061] As shown in FIG. 3, the motor 17 is provided integrally with
the turbo-type compressor 12, which is operated by the rotational
driving power of the motor 17.
[0062] The rotational power of the rotation shaft 35 of the motor
17 is transmitted to the rotation shaft 41 which constitutes the
turbo-type compressor 12 by means of engaged transmission gears 36
and 37, thereby operating the rotation shaft 41 of the turbo-type
compressor 12.
[0063] The turbo-type compressor 12 is designed so that one end
side thereof is designated as the intake opening 42, and the
refrigerant from the vaporizer 11 is thereby output to the intake
opening 42. Intake vanes 40 are disposed at the intake opening 42
so that the intake vanes 40 control the intake volume of the
refrigerant at the intake opening 42.
[0064] The turbo-type compressor 12 is provided with a first stage
compression section 43, and a second stage compression section 44,
in that order, from the intake opening 42 side, and provided on the
first stage compression section 43 and the second stage compression
section 44 are the first stage impeller 19a and the second stage
impeller 19b described above.
[0065] Then, by rotating the rotation shaft 41, the first stage
impeller 19a and the second stage impeller 19b are respectively
rotated, and the refrigerant from the vaporizer 11 is withdrawn
into the first stage compression section 43 from the intake opening
42, compressed by the first stage impeller 19a of the first stage
compression section 43, output to the second compression section 44
via the return passage 49 which includes the diffuser section 46,
return bend section 47 and the return vane 48, and is compressed by
the second impeller 19b of the second compression section 44. After
that, the refrigerant passes through the diffuser section 46 and is
discharged from the discharge opening 53 via the scroll section 52,
which is a fluid passage formed in the circumference direction, to
be sent to the condenser 13.
[0066] As described above, the refrigerant sent from the
intermediate cooler 15 is output to the second stage compression
section 44, and is compressed together with the refrigerant output
from the first stage compression section 43 by the second stage
impeller 19b of the second stage compression section 44. Then, the
refrigerant, as described above, passes through the diffuser
section 46 and is discharged from the discharge opening 53 via the
scroll section 52, to be sent to the condenser 13.
[0067] Next, the structure of the diffuser section 46 in the first
stage compression section 43 and the second compression section 44
will be explained by using the structure of the diffuser section 46
in the first stage compression section 43 as an example.
[0068] As shown in FIG. 4, in the diffuser section 46, the first
wall section 56 that includes the casing 55 of the turbo-type
compressor 12, and the second wall section 58 that includes the
partition plate 57 are formed in such a way to separate from each
other in the radial direction, and in so doing, the diffuser
section 46 is formed in a tapered shape so as to widen gradually
from the inlet opening 46a towards the outlet opening 46b, with the
result that the width dimension of the diffuser section 46 in the
axial direction becomes gradually wider towards the outer radial
direction.
[0069] As described above, the turbo-type compressor 12 is formed
in such a way that, in the diffuser section 46, the width dimension
b2 of the outlet opening 46b is wider than the width dimension b1
of the inlet opening 46a (b1<b2), and therefore, the aspect
ratio of the inlet opening 46a and the outlet opening 46b of the
diffuser section 46 is somewhat reduced and the area ratio of the
inlet opening 46a to the outlet opening 46b of the diffuser section
46 is increased.
[0070] By adopting such a design, as shown in FIG. 5, in the case
of the turbo-type compressor 12 having the diffuser section 46, the
pressure recovery coefficient Cp is increased to a point located at
the left and above the 0.5 value which is higher than the Cp
exhibited by the conventional turbo-type compressor having the
diffuser section 6 in which the width dimension of the inlet
opening 46a is the same as that of the outlet opening 46b, and
therefore, the performance of the diffuser section 46 is enhanced
and the efficiency of the turbo-type compressor 12 is improved.
[0071] Similarly, the pressure recovery coefficient Cp is also
improved in the diffuser section 46 of the second stage compression
section 44.
[0072] Note that although only a two-stage (multi-stage type)
turbo-type compressor having the first stage impeller 19a and the
second stage impeller 19b is explained above, it is obvious that
the present invention may be applied to a singe-stage turbo-type
compressor having one impeller.
[0073] As explained above, according to the turbo-type compressor
12 having the structure described above, because the width
dimensions in the axial direction at the inlet opening 46a side and
the outlet opening 46b side of the diffuser section 46 are made in
such a way that the width of the outlet opening 46b side is larger
than that of the inlet opening 46a side, the aspect ratio at the
inlet opening 46a side and the outlet opening 46b side is made
somewhat smaller and the area ratio thereof is made larger, so that
it is possible to increase the pressure recovery coefficient Cp at
the diffuser section 46.
[0074] In other words, without making the structure complex, it
becomes possible to efficiently recover a dynamic pressure of the
compressed refrigerant, which is output from the first stage
impeller 19a and the second stage impeller 19b, in the form of a
static pressure in the diffuser section 46, and accordingly, the
turbo-type compressor 12 having a superior compression efficiency
may be realized without making the apparatus larger or more
complex.
[0075] Also, the tapered shape of the pair of wall sections,
comprised by the first wall section 56 and the second wall section
58, which constitute the diffuser section 46, readily enables
improvement in the performance by enlarging the width dimension of
the outlet opening relative to that of the inlet opening. Also,
because the first wall section 56 and the second wall section 58
are tapered, it is possible to eliminate a problem of separation of
the refrigerant in the diffuser section 46, which is output from
the first stage impeller 19a and the second stage impeller 19b.
[0076] Also, since the turbo-type compressor 12 described above is
a two-stage type (multi-stage type) having the first stage impeller
19a and the second stage impeller 19b, and the pressure recovery
coefficient Cp is made larger at the diffuser section 46, which is
the passage for the refrigerant output from the first stage
impeller 19a and the second stage impeller 19b, an extremely high
efficiency turbo-type compressor may be realized, in which the
efficiency has been increased in the first stage impeller 19a as
well as in the second stage impeller 19b.
[0077] According to the refrigeration apparatus having the
turbo-type compressor 12 explained above, because the highly
efficient turbo-type compressor 12 having the diffuser section 46,
which exhibits a superior performance in terms of the high pressure
recovery coefficient Cp, is used, it becomes possible to
significantly increase the cooling efficiency to provide a
refrigeration apparatus having superior cooling
characteristics.
[0078] Next, other embodiments according to the invention will be
explained.
[0079] As shown in FIG. 6, in the case of this diffuser section 46
also, the first wall section 56 comprised by the casing 55 of the
turbo-type compressor 12 and the second wall section 58 comprised
by the partition plate 56 are disposed in such a way to separate
from each other towards the outer radial direction to form a
tapered diffuser section 46 that widens from the inlet opening 46a
towards the outlet opening 46b, so that the width dimension of the
diffuser section 46 gradually becomes wider towards the outer
radial direction.
[0080] However, in this diffuser section 46, by making the radius
R2 smaller at the outlet opening 46b, the area ratio of the inlet
opening 46a to the outlet opening 46b is kept the same as the area
ratio prior to the improvement.
[0081] In other words, the area ratio is left unchanged in this
turbo-type compressor 12 while the aspect ratio is reduced, and
therefore, in the case of the turbo-type compressor 12 having the
diffuser section 46, the pressure recovery coefficient Cp shifts,
as shown in FIG. 7, to the left so as to be above 0.5 as compared
with the Cp of a conventional turbo-type compressor having a
conventional diffuser section, thereby improving the performance of
the diffuser section 46 and increasing the efficiency of the
turbo-type compressor 12.
[0082] Accordingly, in the case of the turbo-type compressor 12
having the above-mentioned structure, because the width dimensions
in the axial direction are such that the outlet opening 46b side is
made larger relative to the inlet opening 46a side without altering
the area ratio of the inlet opening 46a side to the outlet opening
46b side in the diffuser section 46, the aspect ratio of the inlet
opening 46a side and the outlet opening 46b side is reduced so that
the pressure recovery coefficient Cp in the diffuser section 46 can
be made larger.
[0083] In other words, without making the structure complex, it is
possible to efficiently recover a dynamic pressure of the
refrigerant, which is output from the first stage impeller 19a and
the second stage impeller 19b, in the form of a static pressure in
the diffuser section 46, and accordingly, the turbo-type compressor
12 may have a superior compression efficiency without making the
apparatus larger or more complex.
[0084] Further, without altering the area ratio of the inlet
opening 46a to the outlet opening 46b in the diffuser section 46,
the width dimension b2 of the outlet opening 46b is made larger
relative to the width dimension b1 of the inlet opening 46a, that
is, because the radius R2 of the outlet opening 46b is reduced by
an amount corresponding to the increase in the width dimension b2
of the outlet opening 46b, the outer radius can be made smaller and
the cost of the compressor can be reduced.
[0085] Also, because the width dimension b2 of the outlet opening
46b is made larger relative to that of the inlet opening 46a
without altering the area ratio of the inlet opening 46a to the
outlet opening 46b, it becomes possible to assuredly improve the
performance of the compressor 12 by reducing the aspect ratio and
increasing the pressure recovery coefficient Cp.
[0086] Note that although a tapered diffuser section 46 that widens
from the inlet opening 46a towards the outlet opening 46b, and the
width dimension of the diffuser section 46 which gradually becomes
wider towards the outer radial direction are formed by separating
the first wall section 56, which includes the casing 55 of the
turbo-type compressor 12, away from the second wall section 58,
which includes the partition plate 57 towards the outer radial
direction, in all of the above embodiments, the efficiency of the
turbo-type compressor 12 can be increased by increasing the
pressure recovery coefficient Cp so long as the width dimension of
the outlet opening 46b side is made wider than that of the inlet
opening 46a side to an extent that would not cause a separation of
fluid stream in the diffuser section 46.
[0087] Here, in the embodiment shown in FIG. 8, only the second
wall section 58, which includes the partition plate 57, is inclined
to form a tapered shape, and in the embodiment shown in FIG. 9,
only the first wall 56, which includes the casing 55, is inclined
to form a tapered shape. In either case, the degree of tapering is
restricted so as not to cause a stream separation in the diffuser
section 46.
[0088] According to the diffuser section 46 shown in FIG. 8 or 9,
one of the wall sections, i.e., either the first wall section 56 or
the second wall section 58, is tapered and the other wall section
is oriented at substantially right angles to the rotation axis 41,
so that the structure of the compressor may be simplified and the
cost thereof may be reduced as compared with the case where both of
the first wall section 56 and the second wall section 58 are
tapered.
[0089] Here, when the second wall section 58 comprised by the
partition plate 57 is tapered, it is necessary to incline the
partition plate 57 itself towards the rear side so as to secure a
curvature that does not generate a stream separation in the return
bend section 47. However, in the embodiment shown in FIG. 9, since
the second wall section 58 comprised by the partition plate 57 is
oriented at substantially a right angle to the rotation axis 41,
problems such as an increase in the dimension in the axial
direction, resulting from slanting the partition plate 57 towards
the rear side to secure a curvature that does not produce a stream
separation in the return bend section 47, may be eliminated.
Accordingly, it is possible to increase the efficiency of the
compressor without increasing the dimension of the turbo-type
compressor 12 in the axial direction.
[0090] That is, according to the turbo-type compressor 12 explained
above, by tapering only one of the pair of wall sections, i.e.,
either the first wall section 56 or the second wall section 58,
which constitute the diffuser section 46, the performance thereof
can be improved quite easily by increasing the width dimension b2
of the outlet opening 46b relative to the inlet opening 46a. Also,
because only one of the wall sections, either the first wall
section 56 or the second wall section 58, needs to be tapered, the
performance of the compressor 12 can be improved even more
simply.
[0091] In particular, in the embodiment shown in FIG. 9, as
described earlier, since the first wall section 56 is tapered,
which constitutes the front side wall section that is more spacious
as compared with the rear side of the impeller 19 that has a
downstream side passage communicating with the diffuser section 46,
the dimension in the axial direction can be made smaller.
[0092] Moreover, it is obvious that the structures of the diffuser
section 46 shown in FIGS. 8 and 9 can be adapted to either of the
structures of the diffuser section 46 shown in FIGS. 4 and 6.
[0093] Further, in the above embodiments, although the diffuser
section 46 is illustrated using a vaneless type diffuser that has
no vanes, the diffuser section 46 used in the present invention may
be provided with vanes.
INDUSTRIAL APPLICABILITY
[0094] As explained above, according to the turbo-type compressor
and the refrigeration apparatus provided with the turbo-type
compressor of the present invention, the following effects may be
obtained.
[0095] According to the turbo-type compressor of claim 1, since the
width dimensions of the openings in the axial direction of the
inlet side and the outlet side are made so that the outlet side is
larger relative to the inlet side, the aspect ratio of the inlet
side and the outlet side is made somewhat smaller and the area
ratio is made larger, so that the pressure recovery coefficient in
the diffuser section can be made larger. This design enables
effective recovery of the dynamic pressure of the compressed fluid
output from the impeller into a static pressure in the diffuser
section without making the structure larger or more complex, and
accordingly, a high compression efficiency is realized in the
turbo-type compressor of the present invention.
[0096] According to the turbo-type compressor of claim 2, without
altering the area ratio of the inlet opening to the outlet opening
in the diffuser section, the width dimension of the outlet opening
is made larger relative to the width dimension of the inlet
opening. That is, because the radius of the outlet opening is
reduced by an amount corresponding to the increase in the width
dimension of the outlet opening, the outer radius can be made
smaller and the cost of the compressor can be reduced.
[0097] Also, even if the area ratio of the inlet opening to the
outlet opening is not altered, because the width dimension of the
outlet opening is made larger relative to that of the inlet
opening, the aspect ratio is reduced, the pressure recovery
coefficient is made larger so as to reliably improve the
performance.
[0098] According to the turbo-type compressor of claim 3, by
tapering the pair of wall sections forming the diffuser section,
the performance of the compressor is readily improved by enlarging
the width dimension of the outlet opening relative to that of the
inlet opening. Also, because the wall sections are tapered, it is
possible to eliminate a problem of stream separation in the
diffuser section of the refrigerant output from the impeller.
[0099] According to the turbo-type compressor of claim 4, by making
only one of the wall sections that constitute the diffuser section,
into a tapered shape, the performance of the compressor can be
improved quite readily by increasing the width dimension of the
outlet opening relative to the inlet opening. Also, because only
one of the wall sections needs to be made into a tapered shape, the
performance can be improved even more easily.
[0100] In particular, by tapering the wall section in the front
side which has more space as compared with the rear side of the
impeller having a downstream side passage that communicates with
the diffuser section, the dimension in the axial direction can be
made smaller.
[0101] According to the turbo-type compressor of claim 5, because
the pressure recovery coefficient is improved in each stage of
compression by respective impellers at the respective diffuser
sections serving as fluid paths for the fluid output by the
respective impellers, a superior multi-stage turbo-type compressor
of high performance may be provided.
[0102] According to the refrigeration apparatus of claim 6, because
a high efficiency turbo-type compressor, having a diffuser section
that exhibits high performance and produces a high recovery
coefficient, is used as a compressor to compress the refrigerant
and to output the compressed refrigerant to the condenser, the
cooling efficiency can be improved significantly, and accordingly,
the refrigeration apparatus can produce superior cooling
performance.
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